Element and process for selectively forming positive or negative

Details Element and process for selectively forming positive or negative Element and process for selectively forming positive or negative

1974-09-03

1976-01-27

Louie, Jr., Won H.

Gas separation: apparatus

Electric field separation apparatus

With means to add charged solid or liquid particles to...

96101, 96107, 96108, 96120, 96 66R, 96 63, 96 64, G03C 504, G03C 128, G03C 136, G03C 530

Patent

active

039350100

ABSTRACT:
My invention is directed to a photographic element capable of forming either a positive or a negative image, depending upon the choice of electromagnetic wavelengths to which it is exposed. The element inludes internally fogged photographic silver halide grains which are substantially free of surface fog. Associated with the grains is a desensitizer containing an imidazoquinoxaline nucleus having a reduction potential more positive than -0.90 volts and an oxidation potential more positive than +0.80 volt. The desensitizer is present in an amount of no more than that required to cover 25 percent of the silver halide grain surfaces. Also associated with the grains is a spectral sensitizing dye having an absorption peak at least 20 nm removed from any absorption peak exhibited by the desensitizer. The photographic element is selectively exposed to electromagnetic radiation of a wavelength to which the silver halide grains are predominantly desensitized or sensitized and then developed in an internal image developer to form either a positive or a negative image.

REFERENCES:
patent: 3772030 (1973-11-01), Gilman et al.
Research Disclosure, Vol. 104, Dec. 1972, Item 10442.

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